1. Field of the Invention
The present invention relates to a semiconductor light emitting device having an end-facet window structure which prevents carrier recombination at a light-exit end facet. The present invention also relates to a process for producing such a semiconductor light emitting device.
2. Description of the Related Art
In conventional semiconductor light emitting devices, when optical output power is increased, currents generated by optical absorption in vicinities of end facets generate heat, i.e., raise the temperature at the end facets. In addition, the raised temperature reduces the semiconductor bandgaps at the end facets, and therefore the optical absorption is further enhanced. That is, a vicious cycle is formed, and the end facet is damaged. This damage is the so-called catastrophic optical mirror damage (COMD). Thus, the maximum optical output power is limited due to the COMD. In order to overcome the above problem, various techniques have been proposed for the window structures which prevent the light absorption in the vicinities of end facets by increasing the semiconductor bandgaps in the vicinities of the end facets.
For example, Japanese Unexamined Patent Publication No. 2000-31596 discloses a semiconductor laser device and a process for producing a semiconductor laser device. In the process, a window structure is realized by removing a portion of an upper cladding layer in a vicinity of light-exit end facet to a depth near a quantum-well active layer by etching, and forming a regrowth layer doped with the same dopant as that of an upper cladding layer so that the dopant diffuses into the quantum-well active layer, and crystal mixture occurs in the quantum-well active layer.
Since, in the above process, the dopant is diffused into the quantum-well active layer through the cladding layer and an optical waveguide layer during the formation of the regrowth layer, the diffusion depth of the dopant and the degree of the crystal mixture vary due to irregularity of thermal diffusion occurring during the formation of the regrowth layer, and therefore the window structure has poor reproducibility. Thus, it is difficult to produce, at a high yield rate, the above semiconductor laser device so that the semiconductor laser device is reliable in a high output power operation. In addition, in the above process, three semiconductor-layer growing steps and two dry etching steps are required to be performed until a semiconductor laser chip is completed. That is, the manufacturing process is complicated, and the manufacturing cost is high.